A polymer electrolyte membrane is a membrane that can conduct electricity through the transport of ions while not conducting electrons to a significant degree. There are a number of types of membranes in use. Some are primarily proton conductors. They can be used in devices ranging from fuel cells to such other types of electrochemical cells. W. M. Risen Jr., in “Ionomers, Characteristic Theory and Application”, edited by Schuamith Schliek, CRC Press, Buca Raton, Fla., 1996, Chapter 12, and all of the references cited therein. Some are primarily metal-containing ion conductors and can be used in applications such as chlor-alkali cells and batteries. Additionally, some are primarily anion conducting membranes and can be used in batteries, separations and other applications.
The membranes range widely in chemical structure. One type of particular interest is the class of proton conductors available for use in fuel cells based on proton conduction in connection with chemical reactions in which hydrogen, alcohols, hydrocarbons and the like are oxidized by an oxygen containing species such as oxygen, air, or a peroxide. Typically, the membrane is in a structure, sometimes called a Proton Membrane Electrode Assembly (sometimes with acronyms such as PEM, MEA, PEMA, PMEA) which contains the membrane and other constituents such as catalysts for the gas reaction, catalysts for dealing with impurities or undesired side reactions, conductors, electrodes, and arrangements for delivering the reactants to the surfaces and removing the products from the surfaces. These are complicated multiphase assemblies and often are prepared by special complex, secret “recipes”. They often are difficult to reproduce and can be unstable in operation. They also have limited surface areas and functionality.
It would be valuable to have a membrane that incorporates a high surface area with the catalytic functionality required for the membrane assembly's operation. For example, in the case of a fuel cell with hydrogen and oxygen, wherein the hydrogen is obtained by reformation or another reaction which leaves some CO in the gas, the catalysts must provide for the catalysis of the hydrogen and oxygen reactions, and preferably also the catalysis of the oxidation of CO.